Incandescent-lamp filament.



. No Drawing.

CHARLES A. Hansen, or SGHENECTADY, NEW YORK,

ASSIGNOR TO GENERAL ELEG- TRIO COMPANY, A CORPORATION OF NEW YOBIL,

moAnnnscENr-LAMr rrumnnr.

Specification of Letters Patent.

Application filed April 8, 1908. Serial No. 425,814. 1

Patented May 14, 1912.

To all whom it may concern:

Be it known that I, CHARLns A. HANSEN, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, havelnvented certain new and useful Improvements in Incandescent-LampFilaments, of which the following is a specifica tion.

In the production of incandescentflamp filaments consisting of tungsten,titanium, zirconium, and similar refractory 1n tals and compounds, ithas been customary. to use some sort of a binding material by the aid ofwhich the powdered refractory metal or material could be shaped intothreads or wires. Some inventors have made use of carbonaceous binders,such as tragaca'nth, sugar solutions, glucose, and starch paste, but theremoval of the carbonaceous residue left by such binders has, ingeneral, proved ditficult and expensive.

According to my present invention, refractory powdered material, such astungsten, is shaped into threads or wires by means of a binder which ona further treatment breaks up or decomposes, and furthermore is of sucha nature and breaks up in such a way that the residue is notinjurious tothe filament and need not be removed therefrom. In fact, the particularbinder hereinafter mentioned as a specific embodiment of my inventionyields a residue of such low conductivity that the completed filamenthas a high specific resistance and can be used on relatively highvoltages.

The binders contemplated by my present invention include those stickymetal oxalates which when highly heated calcine to a stable andrefractory oxid of the metal. Zirconium oxalate is typical of thisclass. Its use in the production of filaments consisting essentially oftungsten is hereinafter described in detail, and will serve to givepersonsskilled in the art a working knowledge of my invention.

Zirconium oxalate can be prepared by precipitation of hot zirconiumnitrate solution with ammonium oxalate. The precipitate is gelatinous incharacter, resembling starch paste in consistency, and has a smooth,even texture. By using ordinary care durlng manufacture, the zirconiumoxalate can be made exceedingly pure.

In making up the mixture of powdered tungsten and zirconium oxalateylmay use ust suflicient oxalate to give tenacity to the mass, or I mayuse a much greater-quantity with the idea of thereby obtaining afilament of articularly high specific resistance.

The p 'astic mass above described can be squirted into wires or threadsin an ordinary manner and should then be' dried and finally heated to ahigh temperature to calcine the oxalate and convert it into zirconiumoxid. This high temperature treatment may be effected by passing currentthrough the filament while supported in a vacuum or suitable gas,theheat treatment being carried far enough to completely sinter andshrink the filaments into a coherent and homogeneous body of tungstenuniformly mixed with zirconium oxid.

As an alternative method of heating, I may make use of the vacuumfurnace shown in United States Patent to March 21, 1905, though I preferto use in place of the graphite heater there shown a heater consistingentirely of tungsten. If desired, the heat treatment in the furnace maybe stopped somewhat short of complete shrinkage, thus ermittingcompletion and shaping of the laments in treating bottles or in the lampbulbs themselves.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The. method of filament manufacture which consists in forming threadsconsisting of a mixture of powdered refractory conductive material witha binder composed essentially of a gelatinous oxalate of a metal havinga stable refractory oxid, and subsequently heating said threads toconvert the oxalate into the oxid and to consolidate the materials intoa coherent conductor.

2. The method of filament manufacture which consists in forming threadsconsisting of refractory metal powder held together by a binder composedessentially of a gelatinous oxalate decom o'sable to yield a refractoryoxid, and heating said threads-in an inert environment to convert theoxalate into oxid and to consolidate and sinter the refractory metal.

Arsen #785,535,

3. The method of filament manufacture which consists in forming threadsconsisting of refractory powder held together by a binder composedessentially of zirconium oxalate, and. subsequently treating thesethreads to convert them into homogeneous conductors containing zirconiumoxid mixed essentially of a metal oxalate decomposable to produce astable refractory oxid.

6. A squirting mixture for lamp filaments consisting of powderedrefractory material and a binder composed essentially of zirco- V niumoxalate.

7. A squirting mixture for lamp filaments consisting of tungsten powderand a binder composed essentially of zirconium oxalate.

8. A squirting mlxture for lamp filaments consisting of tungsten powderand a binder composed essentially of an oxalate decomposable to yield astable refractory oxid.

In witness whereof I have hereunto set my hand this 7th day of April,1908.

CHARLES A. HANSEN.

Witnesses:

HELEN Onrono, BENJAMIN B. HULL.

